U.S. Severe Weather Forecast (Coup d'œil sur la convection)

Day Three

acus01 kwns 300535 
Storm Prediction Center ac 300534 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1234 am CDT sun Aug 30 2015 

Valid 301200z - 311200z 

..there is a marginal risk of severe thunderstorms parts of Montana... 

isolated severe storms with wind and hail may develop across parts 
of Montana this afternoon into mid-evening. 

A progressive shortwave trough near the Washington coast should dampen as it 
reaches the northern Great Plains international border area early Monday. 
Even with dampening...a broad belt of 500-mb swlys at or above 50 knots is 
expected to be centered across the northern rockies and adjacent High 
Plains this afternoon. With very strong upper-level 
flow...hodographs will become rather elongated favoring a 
conditional risk for splitting supercell structures. 

With an initial frontal surge this morning over the northern High 
Plains...afternoon temperatures are expected to be around 10-15 degree 
f cooler compared to Sat across central Montana. Nevertheless...inverted-v 
thermodynamic profiles should remain common but buoyancy will likely 
be meager with MLCAPE only around 250-500 j/kg. Favorable timing of 
middle-level DCVA with respect to the diurnal heating cycle should 
Foster isolated thunderstorms forming over the west-central Montana Mountains in the early 
afternoon. This activity should develop/spread east through the 
afternoon with a risk for isolated severe wind gusts and marginally 
severe hail...before likely diminishing across parts of eastern Montana just 
after sunset. 

..southeast states... 
Scattered thunderstorms should be ongoing along the S Atlantic coast at 12z 
downstream of a persistent upper-level circulation centered near 
Mobile Bay. Convection should develop inland and become widespread 
through the day as the circulation gradually shifts NE towards northern 
Georgia. The best potential for weakly organized convection appears to be 
over parts of central/southern Georgia within a belt of enhanced middle/upper-level 
slys. But given large uncertainty over whether sufficient diabatic 
heating can occur to support a risk for locally damaging 
winds...will defer to later outlooks for possible marginal risk 

.Grams/picca.. 08/30/2015 

Mesoscale Discussion

acus11 kwns 282301 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 282301 

Mesoscale discussion 1754 
National Weather Service Storm Prediction Center Norman OK 
0601 PM CDT Friday Aug 28 2015 

Areas affected...boundary waters of northestern Minnesota 

Concerning...severe potential...watch unlikely 

Valid 282301z - 290100z 

Probability of watch issuance...20 percent 

Summary...isolated severe hail and damaging wind may accompany 
scattered storms developing southeast from Ontario through about 03z. 
Relatively limited spatiotemporal extent and overall amplitude of 
the threat should preclude a Severe Thunderstorm Watch issuance. 

Discussion...a right-moving supercell just north of Rainy Lake appears 
likely to have a severe hail core per recent mrms mesh data within 
increasing thunderstorm development across northwestern Ontario. This activity 
appears to be tied to a weak shortwave impulse evident in water 
vapor imagery crossing the border region that should also be 
supporting an increase in low-level warm air advection per afternoon model forecasts. 
The majority of cams appear a bit overeager with convective 
development thus far. But on the fringe of moderate middle-level wnwlys 
and probable steep middle-level lapse rates...it appears plausible that 
a couple transient supercells and/or a multicell cluster develops 
east-southeast across the boundary waters area through at least sunset. 
Weakening shear with southern extent and increasing mlcin will likely 
result in diminishing intensity towards late evening. 

.Grams/Darrow.. 08/28/2015 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 48759278 48249080 47769091 47419144 47349209 47469282 
47769346 48059380 48619361 48759278